FIG. 1 shows a conventional lighting module 101 based on CoB technology with a carrier plate 102 of aluminum, on the reflective front side 103 of which a number of semiconductor light sources in the form of LED chips 104 have been applied. The use of such a carrier plate 102 has two advantages, to be specific a high reflectivity with at the same time a high thermal conductivity.
The LED chips 104 are electrically insulated with respect to the carrier plate 102 by means of a dielectric chip substrate and are electrically interconnected to one another in series by bonding wires 105. A first LED chip 104, 104h of the series is connected by way of a bonding wire 105 to a first terminal contact 106h, which is at a highest electrical potential HV. A last LED chip 104l of the series is connected to a second terminal contact 106l, which is at a lowest electrical potential LV. The individual LED chips 104 should be interconnected in a series such that the sum of their forward voltages corresponds to the voltage HV-LV applied altogether to this LED series 104h . . . , 104l. 
The front side 103 of the carrier plate 102 is cast along with the LED chips 104 and the bonding wires 105 by means of a light-transmissive casting compound 107, for example silicone or epoxy resin, which may for example include a filler such as diffuser particles and/or phosphor particles.
Since the carrier plate 102 is electrically conductive, it is less suitable for using the lighting module 101 with a high voltage HV-LV applied to the series 104h . . . 104l of LED chips 104 or with a high voltage HV-LV applied to the terminal contacts 106h, 106l. The high voltage may for example correspond to a peak voltage of an alternating voltage signal or correspond to a direct voltage.
Since the thickness of an LED chip 104 is comparatively small (typically in the range of a few 100 micrometers), the application of a high voltage HV-LV leads to a strong electrical field F between the bonding wire 105 and the chip substrate of the LED chip 104 through the casting compound 106 and the remaining part of the LED chip 104, in particular in the region of the first LED chip 104h. In this case, a secondary electrical path P to the LED series circuit is disadvantageously closed.
A further problem occurs if the carrier plate 102 is connected by its rear side 108 to a metallic heat sink 110 by way of an electrically insulating intermediate layer 109, as shown in FIG. 2. The heat sink 110 is typically electrically connected to ground GND. In this case, a capacitive coupling also occurs between the bonding wires 105 and the heat sink 110.
As shown in the equivalent circuit diagram from FIG. 3, corresponding to FIG. 2, for each bonding wire 105 there are at least two capacitances between this bonding wire 105 and the heat sink 110, to be specific a first capacitance Cws between the bonding wire 105 and the carrier plate 102, which includes the casting compound 107 as a dielectric, and a second capacitance Csh between the carrier plate 102 and the heat sink 110, which includes the intermediate layer 109 as a dielectric. The first capacitance Cws is typically considerably smaller than the second capacitance Csh. As a result, the electrical potential at the bonding wire 105 drops across the first capacitance Cws significantly. This additionally leads to a strong electrical field through the casting compound 107.
A known measure for obviating these problems is the use of carrier plates of thermally conductive but electrically insulating ceramic material, for example of AlN. However, this solution is very expensive.